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Monday, August 13, 2018 at 11:00am to 12:30pm
Clark Hall, 609 Clark Hall
Eric Spanton, California Nanosystems Institute, UC Santa Barbara, Santa Barbara, CA, will present seminar. Professor Katja Nowack, host.
Seminar Title: Strongly correlated ‘fractional Chern insulators’ in graphene heterostructures
Abstract: Graphene is a highly tunable platform for studying the effects of electron-electron interactions in two dimensions. Encapsulation with a 2D dielectric (hexagonal boron nitride, hBN), and more recently the use of single-crystal graphite top and bottom gates have decreased the electronic disorder to a level suitable for the study of fragile and exotic strongly correlated states. Additionally, control of twist angle between closely-matched crystal lattices allows for unique control of electronic properties, leading to the “Hofstadter butterfly” and more recently unconventional superconductivity. I will describe the first experimental observation of a class of states in nearly aligned hBN/graphene heterostructures called fractional Chern insulators (FCIs), a close relative of the fractional quantum Hall effect. In graphene, FCIs arise in the presence of electron-electron interactions, high magnetic fields, and a long wavelength ‘moire’ superlattice formed by close alignment between hBN and graphene lattices. Twist angle between graphene and hBN, electron density and perpendicular electric field tune the underlying single-particle bands to realize different types of FCIs. The realization of FCIs opens the door for the study of novel topological phase transitions and exotic defect states.